Bridget Jones's Diary was the defining novel for the self-obsessed 1990s. Bridget's endless calorie, cigarette and wine unit counting were the intro to every chapter. Now Bridget is back in a new novel, Mad About the Boy, only this time round she is a mum with a smartphone addiction.

At the time of writing, the pre-publicity does not reveal whether "Bridge" is still logging the minutiae of her consumption.

However, if the new book maintains Bridget's neurosis, then by rights she will be sporting a Nike FuelBand and tracking her menopausal highs and lows with mood-tracking app Mappiness as part of the global phenomenon that is Quantified Self (QS), or Life Logging, to give it a more user-friendly name.

In essence QS is simply keeping a detailed log of your daily habits, moods and sleeping patterns by inputting information into smartphone apps that can communicate with motion-sensitive wristbands or other wearable gadgets.

There is even a Quantifiedself.com portal that brings together global users and makers of self-tracking tools and apps. The site details and organises international meetings, conferences, community forums and local meet-up groups that endlessly discuss the results of self-tracking and what they mean.

The magic, and potential, of QS is that the technology can aggregate all that information into charts and graphs to, over time, give you a picture of how and where you live your life, what you consume and when, how often you exercise and how you feel. This life "overview", say the experts, could help brands strike gold.

Drew Benvie, founder of social media agency Battenhall, says: "The Quantified Self movement is really not that complex. It's all about people logging details about their lives so that they can benefit in some way, by making improvements in their habits, diet, work life balance or something else.

Technological advancements have turned this cult phenomenon, which started in the US, into a global boom - from apps such as Lift and Moves, to gadgets like Jawbone Up, Fitbit, GoPro and Google Glass.

The opportunity for brands now is to tap into the data the new wave of connected consumers are happy to broadcast so that they can learn more and engage. This is just another step in the evolution of PR into a broader, integrated comms function."

He explains that QS is now riding on a perfect storm of three elements: smartphone technology that has got a lot better at processing data; affordable sensors that can monitor everything from how well we sleep to how far we walk; and digital health - the whole new world of apps and gadgets designed to help us stay healthy.

Tech takes off

And the technology continues to improve apace. The new iPhone 5s, launched just last month, has an in-built accelerometer, gyroscope and compass, with Apple making the functionality available to third-party developers.

Not surprisingly Nike has already confirmed its launch of the Nike+ Move app, which will not only track daily activities but also tie into the Apple Game Centre, meaning users can compete against each other.

Benvie says: "The Quantified Self movement is really only just taking off. We're at the beginning of a massive wave with a huge amount of experimentation."

He adds the role of PR in QS is still a moving feast as the movement's natural affinity currently appears to be with brand marketing departments, but he stresses the potential for PR professionals to embrace QS is huge.

"PR departments have long been the custodians of a brand's reputation. Now, consumers are interacting with brands in new ways, based on data, check-ins, movements and more. Consumers are logging the food they eat, where they go and how they feel. Brand discussions have gone beyond the written word and so PR people need more than just a search engine or a clippings report to understand what this kind of consumer engagement means, let alone how to respond."

He adds: "Social media forced departments that didn't normally work together to talk. PRs are often the first to spot when bad things happen. I think increasingly you'll see tech sat at the next table to PR and the PR teams will become increasingly tech savvy."

The PR industry is still considering how best to employ QS, but Benvie says it will provide deeper, data-driven ways of capturing consumers' attention: "The public is more likely to take part in campaigns that revolve around direct data-driven digital engagement, so planning needs to take a quantum leap forward."

He points to the London School of Economics' research project aiming to quantify the nation's mood at different times of day and days of the week via the Mappiness app. "It has attracted more than one million responses and is the kind of campaign we could easily have seen coming from a consumer brand," he says.

Rhodri Harries is MD at Kaizo, the agency that looks after PR for the health, fitness and sleep tracker Fitbit, which boasts £300m worth of sales in the UK. He says Fitbit, along with other health and fitness gadgets, will revolutionise the way we monitor our lives.

However, he believes using the term Quantified Self bestows more mystery on the technology than it deserves. "Quantified Self is a term used by enthusiasts within the movement and those involved in deep tech. Fitbit's users call it activity tracking. Most won't have heard of QS and I don't think it will be a term we'll be using in a year's time.

"If you look at the London Quantified Self group, there are only 1,000 members - however, we know from research that around 70 per cent of people are monitoring their health in some form. The big difference now is the ability to use that data to motivate ourselves. It is as simple as the more brands know about consumer behaviour, the better they adapt and the more they can sell."

Marc Southern, head of digital healthcare at FleishmanHillard, is one of the few members of London's QS meet-up group. He says mostly members talk about collated fitness or sleep data. "QS is at the beginning of a huge cycle and is mostly the preserve of fitness freaks and geeks ... no one yet has really pulled something together to make it meaningful. It's about getting the balance right between it being a gimmick and being valuable - helping consumers make behavioural changes with simple challenges."

This, he says, could be particularly useful in the healthcare arena where companies are already considering how to help patients over and above simply giving them medication. "Beyond the pill", says Southern, will see healthcare companies use a combination of QS, Big Data and healthcare apps to do this.

Southern says he is working with "a couple" of brands at the conceptual stages of incorporating QS into their consumer comms mix, but stresses the territory is still new.

Rules on data use

There is also the question of how data is used and consumer privacy. "There are people thinking about what QS could look like but the tools are not all in place for it to really work yet," concludes Southern.

And what of brands that do not boast their own fitness or sleep trackers - how will they be able to ride the QS movement? Harries believes non-fitness brands will still be able to tap into the QS movement by developing apps that integrate with activity trackers.

He uses Coca-Cola as a prime example of a brand with no intrinsic health credentials, but one that has already repositioned its marketing to encourage Coke lovers to enjoy it as part of a healthy lifestyle. "I could see a brand like Coke developing an app to integrate with a tracking device. You're going to see a lot more brands with apps that do this."

In fact, in the US, brands are already making inroads into piggy-backing on fitness trackers. US digital agency Kiip has created an in-app system that allows developers to offer branded rewards. It recently launched a "fitness channel" of apps offering branded rewards to users for their achievements.

So there you have it. Quantified Self is little more than a digital version of "Dear diary ..." - deep navel-gazing for the digital age.

And yet it could be so much more.

Battenhall's Benvie sums up the challenge perfectly: "What this all means for the PR person is a more tech-savvy approach to understanding consumer behaviour and figuring out how to capture and capitalise on a new kind of attention."